This invention relates to a sheet feeding apparatus e.g. for feeding a copying machine with copying sheets, more specifically to an apparatus for feeding sheets provided with a detachable sheet storage box.
As a sheet feeding apparatus for feeding a copying machine with copying sheets one by one, there is generally used an apparatus which is provided with a cassette as a sheet storage box to be detachably set in the storage portion inside the housing of the copying machine. According to such a sheet feeding apparatus, the copying sheets in the cassette are fed one by one into the housing by means of sheet feeding rollers as sheet feeding means disposed in the housing. Thereupon, in order to ensure the sheet feeding operation, it is necessary to produce a given friction between the copying sheet and the feeding rollers. Springs are generally used as means for producing the friction. At present, the space for the springs is set inside the cassette according to one type of apparatus, and inside the copying machine according to another. Simpler in construction, the latter type is widely put to practical use.
In the sheet feeding apparatus of the type using the springs in the cassette, however, the sheet feeding rollers must be kept away from the front end edge of a pile of copying sheets stored in the cassette when inserting the cassette into the housing. On the other hand, the sheet feeding rollers need be in contact with the uppermost one of the stored copying sheets on completion of the insertion of the cassette into the housing. It is therefore necessary to provide a mechanism for letting the sheet feeding rollers escape upward lest they should come into contact with the copying sheets inside the housing at the cassette insertion.
Recently, there has been a tendency to reduce the size of the copying machine. The copying machine of the aforementioned type cannot, however, be reduced in height due to the space for letting the sheet feeding rollers escape, thus failing to meet the requirement for the miniaturization.